Crocodiles and Native Updates + Section Bugfixes

Natives now predict trajectories better when throwing spears. Perhaps a
bit too well...
Crocodiles have been modelled and implemented. They will follow the
player after the player has either shot them, bumped into them, or gone
past them (in z value). They will chase at a speed slightly higher than
the boat, and bounce back when shot or when hitting the boat in order to
give a short period in between attacks and a way to keep them away. The
crocodiles also go underwater when they touch a rock, so they don't
appear to clip through the rocks but rather go underneath them.